error LNK2019

[shinigam1]

hey, i keep running into an error problem... What could be causing this?

//bow.h
#include <iostream>
#include <string>

using std::string;



class Bow
{
	
	// data member declarations
	string colour;
	bool drawn;
	int numOfArrows;
public:
	 //constructor
	Bow(string aColour);
 // destructor
 Bow::~Bow();
	// methods
	void draw();
	int fire();

};


//bow.cpp

#include <iostream>
#include <cstring>
#include "bow.h"

class ArcheryCompetition
{
private:
	//memeber variables
	int rounds;
	float redScore;
	Bow red;
	float blueScore;
	Bow blue;
public:
	//constructor
	ArcheryCompetition(int lrounds);

	//destructor
	~ArcheryCompetition();

	//methods
	int compete(void);
};

//constructs an ArcheryCompetition object

ArcheryCompetition::ArcheryCompetition(int lrounds) :
	rounds(lrounds), red(Bow("red")),
		blue(Bow("blue")), redScore(0), blueScore(0)
	{ }

	//the destructor

ArcheryCompetition::~ArcheryCompetition()
{
}

//the heart of the game
//walks the player through an entire competition
//and figures out who won
int ArcheryCompetition::compete()
{
	using std::cout;
	//go through each round, keeping track of the score
	for(int i = 0; i < rounds; i++)
	{
		cout << "now on round " << i+1 << ".\n";
		red.draw();
		blue.draw();
		redScore = (red.fire() + redScore * i)/(i+1) ;
		blueScore = (blue.fire() + redScore * i)/(i+1) ;
	}
	//figure out who won
	if(redScore == blueScore)
		cout << "We have a tie!!!\n";
	else if(redScore < blueScore)
		cout <<"Blue wins her hand!!\n";
	else 
		cout << "red wins her hand!!\n";
	return 1;
}

int main(void)
{
	//the driver function: constructs the object and calls the appropriate methods
	ArcheryCompetition plymouthSquare(2);
	plymouthSquare.compete();
	return 0;
}

the error is shown as:

1>bow.obj : error LNK2019: unresolved external symbol "public: __thiscall Bow::~Bow(void)" (??1Bow@@QAE@XZ) referenced in function "public: __thiscall ArcheryCompetition::ArcheryCompetition(int)" (??0ArcheryCompetition@@QAE@H@Z)

1>bow.obj : error LNK2019: unresolved external symbol "public: __thiscall Bow::Bow(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (??0Bow@@QAE@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) referenced in function "public: __thiscall ArcheryCompetition::ArcheryCompetition(int)" (??0ArcheryCompetition@@QAE@H@Z)

1>bow.obj : error LNK2019: unresolved external symbol "public: int __thiscall Bow::fire(void)" (?fire@Bow@@QAEHXZ) referenced in function "public: int __thiscall ArcheryCompetition::compete(void)" (?compete@ArcheryCompetition@@QAEHXZ)

1>bow.obj : error LNK2019: unresolved external symbol "public: void __thiscall Bow::draw(void)" (?draw@Bow@@QAEXXZ) referenced in function "public: int __thiscall ArcheryCompetition::compete(void)" (?compete@ArcheryCompetition@@QAEHXZ)

1>c:\users\blahblah\documents\visual studio 2010\Projects\test\Debug\test.exe : fatal error LNK1120: 4 unresolved externals

thanks in advanced

[coder777]

What could be causing this?

Nothing from class Bow is implemented. It's supposed to be in bow.cpp, but isn't apparently

[shinigam1]

ahh okay, is there any reason why nothing from class bow is being implemented, have i missed something?

[eraggo]

//bow.h
#include <iostream>
#include <string>

using std::string;



class Bow
{
	
	// data member declarations
	string colour;
	bool drawn;
	int numOfArrows;
public:
	 //constructor
	Bow(string aColour);
 // destructor
 Bow::~Bow();
	// methods
	void draw();
	int fire();

};


//bow.cpp

#include <iostream>
#include <cstring>
#include "bow.h"

class ArcheryCompetition
{
private:
	//memeber variables
	int rounds;
	float redScore;
	Bow red;
	float blueScore;
	Bow blue;
public:
	//constructor
	ArcheryCompetition(int lrounds);

	//destructor
	~ArcheryCompetition();

	//methods
	int compete(void);
};

//constructs an ArcheryCompetition object

ArcheryCompetition::ArcheryCompetition(int lrounds) :
	rounds(lrounds), red(Bow("red")),
		blue(Bow("blue")), redScore(0), blueScore(0)
	{ }

	//the destructor

ArcheryCompetition::~ArcheryCompetition()
{
}

//the heart of the game
//walks the player through an entire competition
//and figures out who won
int ArcheryCompetition::compete()
{
	using std::cout;
	//go through each round, keeping track of the score
	for(int i = 0; i < rounds; i++)
	{
		cout << "now on round " << i+1 << ".\n";
		red.draw();
		blue.draw();
		redScore = (red.fire() + redScore * i)/(i+1) ;
		blueScore = (blue.fire() + redScore * i)/(i+1) ;
	}
	//figure out who won
	if(redScore == blueScore)
		cout << "We have a tie!!!\n";
	else if(redScore < blueScore)
		cout <<"Blue wins her hand!!\n";
	else 
		cout << "red wins her hand!!\n";
	return 1;
}

int main(void)
{
	//the driver function: constructs the object and calls the appropriate methods
	ArcheryCompetition plymouthSquare(2);
	plymouthSquare.compete();
	return 0;
}

Line 21: Remove Bow::-part This is not used inside a Bow-class definition itself.

How actually you use your bow-class? i mean... where you define all methods for that class? I mean where is your implementations of these?

Bow::Bow(string aColour);
Bow::~Bow();
void Bow::draw();
int Bow::fire();

Adding more as/if i find them

Rule of thumb: create class "prototype" in the header file (.h) and the implementation in source file (.cpp). DO NOT implement another classes in other classes source file :)

[coder777]

Your code is supposed to look something along this:

//bow.h
#include <iostream>
#include <string>

using std::string;



class Bow
{
	
	// data member declarations
	string colour;
	bool drawn;
	int numOfArrows;
public:
	 //constructor
	Bow(string aColour);
 // destructor
 Bow::~Bow();
	// methods
	void draw();
	int fire();

};


//bow.cpp

Bow::Bow(string aColour)
{
... // Your implementation
}

// destructor
Bow::~Bow()
{
 // Your implementation
}

// methods
void Bow::draw()
{
... // Your implementation
}

int Bow::fire()
{
... // Your implementation
}


// ArcheryCompetition.h

#include <iostream>
#include <cstring>
#include "bow.h"

class ArcheryCompetition
{
private:
	//memeber variables
	int rounds;
	float redScore;
	Bow red;
	float blueScore;
	Bow blue;
public:
	//constructor
	ArcheryCompetition(int lrounds);

	//destructor
	~ArcheryCompetition();

	//methods
	int compete(void);
};

// ArcheryCompetition.cpp

//constructs an ArcheryCompetition object

ArcheryCompetition::ArcheryCompetition(int lrounds) :
	rounds(lrounds), red(Bow("red")),
		blue(Bow("blue")), redScore(0), blueScore(0)
	{ }

	//the destructor

ArcheryCompetition::~ArcheryCompetition()
{
}

//the heart of the game
//walks the player through an entire competition
//and figures out who won
int ArcheryCompetition::compete()
{
	using std::cout;
	//go through each round, keeping track of the score
	for(int i = 0; i < rounds; i++)
	{
		cout << "now on round " << i+1 << ".\n";
		red.draw();
		blue.draw();
		redScore = (red.fire() + redScore * i)/(i+1) ;
		blueScore = (blue.fire() + redScore * i)/(i+1) ;
	}
	//figure out who won
	if(redScore == blueScore)
		cout << "We have a tie!!!\n";
	else if(redScore < blueScore)
		cout <<"Blue wins her hand!!\n";
	else 
		cout << "red wins her hand!!\n";
	return 1;
}

// main.cpp

int main(void)
{
	//the driver function: constructs the object and calls the appropriate methods
	ArcheryCompetition plymouthSquare(2);
	plymouthSquare.compete();
	return 0;
}